This invention relates to a rotary actuator which converts electrical energy into a controlled force of rotation.
In devices for separating or sorting sheets of paper, it is customary to use a blade changeover mechanism as shown in FIGS. 2 and 3. FIG. 2 is an inclined view of such a mechanism in a conventional device. In the FIG., 1 is a plunger type solenoid, 1a is a plunger, 2 is a link, 3 is a lever, 4 is a shaft, 5 are blades, and 6 is a restoring spring. When the solenoid 1 is energized, the plunger 1a is a attracted to the solenoid 1 and the link 2 moves together with it in the direction A. The upper edge of lever 3 is then moved in direction A, and the shaft 4 rotates together with the blades 5 in direction B. FIG. 3 illustrates the case when the above paper sheet sorter is incorporated in a paper sheet transport path 7. When the solenoid 1 is energized, the position of blade 5 moves from FIG. 3 solid line in the figure to that of the dotted line, and paper sheets transported by roller 8 from side C are sent to the path D.
When solenoid 1 is de-energized, however, the upper edge of lever 3 returns in the direction E under the action of a restoring spring 6 which is attached between the lever 3 and the housing (not shown in the figure) under a specified tension. Shaft 4 then rotates in direction F, blade 5 moves from the position of the dotted line in the figure to that of the solid line, and paper sheets transported by roller 8 are sent to the path G.
A rotary solenoid as shown in FIG. 4, may be used in place of the plunger solenoid 1. This figure is a partial cut-away inclined view of a rotary solenoid 10. The stationary assembly consists of a case 11, base 12 and coil 13; the moving assembly consists of a rotor 14, and a shaft 15 fixed to the rotor 14.
A groove 16 (ball race) of substantially semi-circular cross-section in the upper part of case 11 extends in the direction of rotation H of the rotor 14. Several balls (not shown in FIG. 4) are interposed between rotor 14 and case 11 in ball race 16 such that they are free to turn, and support rotor 14 such that it can rotate. Further, the bottom of ball race 16 is sloped with respect to the direction H so that its depth gradually increases. With this arrangement, rotor 14 is pulled in direction I when coil 13 is energized, and rotates in the direction H in which the depth of ball race 16 becomes greater. When coil 13 is de-energized, rotor 14 rotates in the direction opposite to direction H under the action of a restoring spring (not shown in FIG. 4), and returns to its original position.
In these conventional structures, however, the following problems arise.
In the structure shown in FIG. 2, a mechanism such as the link 2 or lever 3 is necessary to convert the linear motion of plunger 1a into a rotary motion, and a large number of structural parts are required. The area for installing these structural components is therefore large, which is an effective obstacle to making the device compact. Further, the attraction of plunger 1a must overcome the restoring force of spring 6. Due to the considerable forces involved, rebound occurs easily, and it can also occur easily when the plunger 1a returns. It is thus difficult to obtain a stable action of the blades 5, with the result that the mechanism often jams when it is incorporated in a paper sheet sorter.
In the structure shown in FIG. 4, also, while there is no need for a mechanism to convert linear motion to rotary motion and while there is a smaller number of structural components, the ball race 16 has to be machined very precisely when the rotary solenoid 10 is manufactured and due to the difficulty of manufacture, the price of the assembly becomes high. Further, as a rotation is given in opposition to the restoring spring 6, the speed of rotation is low, and so processing speed is also low when the rotary selenoid 10 is incorporated in a paper sheet sortor.